Come up with an simple action example which uses cocoapods

As discussed in #26 we need some solution for managing and sharing extensions outside of the
main GH repo.

Let's try to get a cocoapods enabled simple example action going.

Start with the requirements discussed in issue #26 and the request for a CocoaPods-enabled simple example action. Define what managing and sharing extensions outside the main GitHub repository should mean, then verify that the example can be used through CocoaPods.

Written by the indexing model from the issue text.